JPH0655211B2 - Ultrasonic Doppler blood flow meter - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ultrasonic Doppler blood flow meter used for measuring blood flow velocity in a living body in the medical field.

2. Description of the Related Art In recent years, ultrasonic Doppler blood flowmeters have become popular in the medical field such as the heart and circulatory organs. This ultrasonic Doppler blood flow meter obtains blood flow velocity information by transmitting ultrasonic waves into a living body and performing Doppler shift of a reflected echo signal received by a moving object such as a blood flow. The Doppler shift frequency fd of the echo signal received by the object in which the transmitted ultrasonic signal f moves at the velocity V is expressed by the following equation.

fd = z · V · f / c cos θ (1) In the above equation (1), c is the speed of sound and θ is the angle between the moving direction of the object and the ultrasonic wave traveling direction.

Generally, to detect a Doppler signal, the received echo signal is quadrature-detected at a frequency f. The detected Doppler signal is frequency-analyzed, the frequency and amplitude are displayed on the image, and the sound signal is directly output from the speaker. In the diagnosis, the blood flow information displayed on the image is mainly used. On the other hand, the Doppler signal output from the speaker is also used for searching the blood flow position, and the diagnosis is performed by a subtle change in the sound included in the Doppler signal, which is very important information.

Problems to be Solved by the Invention However, recently, in order to achieve high resolution, the frequency of ultrasonic waves used tends to increase. That is, (1) above
Since f shown in the equation becomes high, the Doppler shift frequency fd also becomes proportionally high. For example, the Doppler shift frequency fd of an echo signal received by an object moving at a speed of 3.5 mHz at a speed of 1 m / sec is about 4.5 KHz, but if a 10 MHz ultrasound is used, the Doppler shift frequency is
fd becomes as high as 13 KHz, which is close to the limit of human audible frequency, and it becomes impossible to use the blood flow information included in the Doppler signal for diagnosis. Similarly, in the measurement of high-speed blood flow, the Doppler shift frequency fd may be close to or higher than the audible frequency limit, which is a diagnostic problem.

The present invention solves the above-mentioned conventional problems, and uses high-frequency ultrasonic waves, and when performing high-speed blood flow measurement, compresses the Doppler shift frequency within the audible frequency to perform diagnosis by a voice signal. An object is to provide an ultrasonic Doppler blood flow meter that can be performed.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention obtains a Doppler signal from a means for transmitting an ultrasonic wave into a living body and receiving an echo signal reflected in the living body, and a means for receiving the echo signal. A Doppler signal detection unit and a band compression circuit that sequentially stores the Doppler signals obtained by the Doppler signal detection unit and sequentially reads the Doppler signals at a speed slower than the writing speed during storage are provided.

Operation The present invention has the following effects due to the above configuration. That is, the band compression circuit sequentially stores the Doppler signals, and sequentially reads the Doppler signals at a speed slower than the writing speed at the time of storage, so the frequency of the Doppler signals is lowered,
It can be compressed into the audio frequency.

Examples Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a block circuit diagram showing an ultrasonic Doppler blood flow meter in one embodiment of the present invention.

In FIG. 1, 1 is a probe that transmits ultrasonic waves into the living body A and receives an echo signal from the inside of the living body A. 2 is a probe that transmits and receives to and from the echo signal received from the probe 1 and is a Doppler signal. To display the Doppler signal detected by the Doppler signal detection unit 2 in a format such as a sonargram, CRT and 4 output from the Doppler signal detection unit 2. A band compression circuit for band-compressing the Doppler signal D, and an A / D for A / D converting the Doppler signal D.
A converter 5, a memory circuit 6 including a digital memory for storing the A / D-converted Doppler signal Dd, a write pointer 7 indicating a position for writing the Doppler signal Dd, A /
The clock generation circuit 8 for generating the sampling clock of the D converter 5, the first read pointer 9a indicating the position of the first Doppler signal Da read from the memory circuit 6, and the position of the second Doppler signal Db read from the memory circuit 6 are displayed. The second read pointer 9b, the first and second gain variable circuits 10a and 10b, and the first and second gain variable circuits 10a for amplifying or attenuating the first and second Doppler signals Da and Db, respectively. , 10b for controlling the gain control circuit 11 and the adder circuit 1 for adding both the Doppler signals Ga · Da, Gb · Db gain-adjusted by the first and second variable gain circuits 10a, 10b.
2. The control circuit 13 controls each part. Reference numeral 14 is a D / A converter, 15 is an audio amplifier circuit, and 16 is a speaker.

Next, the operation of the above embodiment will be described.

The echo signal received by the probe 1 is detected by the Doppler signal detector 2 and output as a Doppler signal D. Also,
Inside the Doppler signal detection unit 2, signal processing is performed on the Doppler signal D, and it is displayed on the CRT 3 as a spectrum distribution. In the band compression circuit 4, the A / D converter 5
The A / D conversion is performed on the Doppler signal D, and the A / D converted Doppler signal Dd is stored in the storage circuit 6. At the time of A / D conversion, the sampling clock Tw output from the clock generation circuit 8 is used to write data to the address of the storage circuit 6 indicated by the write pointer 7. The write pointer 7 is incremented at every sampling clock Tw to change the write address W ₁ . On the other hand, the first
The second read pointers 9a and 9b indicate different addresses and are incremented in synchronization with the read sampling clock Tr. Each read pointer 9a, 9
The Doppler signals Da and Db at the address indicated by b are controlled by the gain control circuit 11 into the first and second gain variable circuits 10a,
The amplitude is controlled by 10b, and the Doppler signals Ga, Da, Gb
-Add Db with the adder circuit 12. This Doppler signal Dc
Is D / A converted by the D / A converter 14, amplified by the amplifier circuit 15, and output from the speaker 16.

The operation of the band compression circuit 4 will be described in more detail with reference to FIG.

FIG. 2 is a time chart showing an example in which the Doppler signal D input to the band compression circuit 4 in FIG. 1 is compressed to a frequency of 1/3 and output. In the figure, the Doppler signal, which is a digital quantity, is shown as an analog quantity for the sake of explanation.

The write point W value output by the write pointer 7 is incremented with the lapse of time, and the Doppler signal Dd value is written from left to right as shown in FIG. 2 (a).
When the write point value W indicates the address P ₀ , the first
The read point value Ra output from the read pointer 9a of FIG. 2 is loaded with the write point value W, and the Doppler signal Dd value is read from the address P ₀ by three times as long as the write time as shown in FIG. 2 (b). . This reading ends when the read point value Ra reaches the address P ₁ . At this time, the write point value W output by the write pointer 7 has advanced to P ₃ . If the time required to write from address P _{0 to} P ₁ is T, it takes 3 to read.
Since it takes T time, the frequency is compressed to 1/3. On the other hand, as shown in FIG. 2 (c), the second read pointer 9b reads from the place where the write point value is P ₂ to P ₃ by taking three times as long as the time of writing. Therefore, the point values Ra and R of the read pointers 9a and 9b, respectively.
The Doppler signals Da and Db read out in b appear alternately, and this and the second signal generated by the gain control circuit 11 are generated.
The control signals Ga and Gb shown in FIGS.
If multiplied by a and 10b, Ga · D shown in FIGS. 2 (f) and 2 (g)
Two Doppler signals a and Gb · Db are obtained. By adding these by the adder circuit 12, the Doppler signal Dc band-compressed to 1/3 is obtained as shown in FIG. 2 (h).

It should be noted that the gain control signals Ga and Gb shown in FIGS.
Is a trapezoidal wave, but a Hamming wave, a Gaussian wave, or the like may be used. Further, the Doppler signal Dc read out from the band compression circuit 4 has thinned out the waveform of the original Doppler signal D, and information is actually lost, but there is no sense of discomfort in terms of hearing. Also, the period for outputting a Doppler signal Da and Db are alternately approximately 10 to 100 m _sec is appropriate.

In the above embodiment, the case where the memory circuit 6 is a digital memory has been described, but an analog memory element such as BBO may be used. Even with the existing Doppler blood flow meter, the same effect can be obtained by connecting only the band compression circuit 4 as an adapter. When outputting a Doppler signal as a stereo sound, the above configuration may be used for 2 channels.

As described above, according to the Doppler blood flow meter of the present invention,
Since the band compression circuit sequentially stores the Doppler signals and sequentially reads the Doppler signals at a speed slower than the writing speed at the time of storage, the frequency of the Doppler signals can be lowered and compressed within the audible frequency. Therefore, even a Doppler signal outside the audible band can be converted into the audible band,
When high-frequency ultrasonic waves are used and high-speed blood flow measurement is performed, it is possible to make a diagnosis using a voice signal, and more accurate diagnosis information can be obtained.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an ultrasonic Doppler blood flow meter in one embodiment of the present invention, and FIG. 2 is a timing chart for explaining the operation of the above embodiment. 1 ... probe, 2 ... Doppler signal detector, 3 ... C
RT, 4 ... band compression circuit, 5 ... A / D converter,
6 ... Memory circuit, 7 ... Write pointer, 8 ... Clock generation circuit, 9a, 9b ... Read pointer, 10
a, 10b ... Gain variable circuit, 11 ... Gain control circuit, 12 ...
… Adding circuit, 13 …… Control circuit, 14 …… D / A converter, 15 …… Amplifying circuit, 16 …… Speaker.

Claims (3)

[Claims] 1. A means for transmitting an ultrasonic wave into a living body and receiving an echo signal reflected in the living body, a Doppler signal detecting section for obtaining a Doppler signal from the received echo signal, and a Doppler signal detecting section Sequentially store the Doppler signal,
An ultrasonic Doppler blood flow meter, comprising: a band compression circuit that sequentially reads at a speed slower than a writing speed during storage. 2. A storage circuit in which a band compression circuit stores a Doppler signal, a write pointer indicating a storage position of the storage circuit, a plurality of read pointers indicating a read position from the storage circuit, and these read pointers. A plurality of gain variable circuits for amplifying or attenuating the Doppler signals stored in the positions shown, a gain control circuit for controlling these gain variable circuits, and an addition for adding the Doppler signals output from the gain variable circuits. The ultrasonic Doppler blood flowmeter according to claim 1, further comprising means. 3. A digital memory is used for the memory circuit,
The ultrasonic Doppler blood flow meter according to claim 2, wherein an A / D converter is used for its input.